1. Field of the Invention
This invention relates to improvements in valves and control systems, particularly those adaptable for use in a material handling system of the type utilizing a dual walled cup-shaped inflatable bag.
2. Prior Art
In commonly owned co-pending applications, Ser. No. 257,604 filed Apr. 27, 1981, now U.S. Pat. No. 4,421,250 of Dec. 20, 1983, Ser No. 307,089 filed Sept. 30, 1982, now U.S. Pat. No. 4,449,649 of May 22, 1984, Ser. No. 357,589 filed Mar. 12, 1982, Ser. No. 357,592 filed Mar. 12, 1982, and PCT International Publication No. W082/03839 of Nov. 11, 1982, there are disclosed systems of handling, storing, and discharging free-flowing granular material utilizing a generally cup-shaped, dual walled, inflatable bag for assisting in the discharge of material after it assumes its angle of repose following gravity discharge. In connection with the development of the inventions disclosed in the co-pending applications, it was discovered that there were no suitable valve assemblies and controls needed for controlling the high volume, low pressure air flow required for inflating or deflating the bag.
British Pat. No. 1,144,162 discloses a lined silo in which the liner is expanded by pressure to assist gravity discharge. The fluid pressure control components are shown schematically as a pump, compressor, and three-way valve alternatively connecting the space between the liner and the rigid wall to the pump or compressor. This arrangement has disadvantages in that it lacks automatic controls, lacks means for sensing the end of inflation and deflation cycles, and utilizes extra and unneeded components.
There is a need in the art for a relatively high-volume, low-pressure four conduit fluid flow control valve assembly which can be switched automatically from one cycle to another, i.e., from the inflation cycle to the deflation cycle. It is highy desirable to utilize other than manual controls for changing cycles and to have the valves controlling the conduits through which the inflating and deflating air passes operate quickly and reliably to handle the large volume of low pressure air from a fan or the like.